Thanks for the input. The longitudinal flip may indeed take less torque, because the hulls become partially submerged, and its a good probability that the mast is no longer there to use as a fulcrum.

Yeah, the 20 degree heel in the first righting pull is probably too small--however, you will be past the maximum righting moment, so it will probably just keep coming up until the bag takes the load.

I did worry a bit about the load on the mast tip from the bag, but I figured that it was stout enough to take 1000 lbs unsupported. If you're worried, put two bags at the shroud connection. Hell, if the Antares 44 mast is designed for twice the boat's displacement, maybe I would just keep adding lift bags at the shroud connection until something happened.

The water in the hulls could be a deal killer. I'd open all the deck hatches, but there could still be enough water trapped to break things. Reminds me of the time I used a halyard on a big boat to pull a double bottom dinghy out of the water where water had entered the double bottom space. I raised it slowly, but at some point the two bottoms separated like a zipper and we had a big repair job to do.

It takes substantially less effort to right a cat end over end, as you don't lift water due to flooding, and part of empty weight is supported by buoyancy, not just the force you apply. That is far more significant than the beam being less than length.
The leverage of the cat weight and buoyancy produce therefore substantially less righting moment longitudinally than than a cat with no water inside. could easily be 90% less.

Interestingly challenge...I used to flip flooded 30ft x 90ft flat barges longitudinally on a regular basis in order to clean and do repairs.

We used long Bridles made fat to front bollards..that then went under the bottom then aft and up on deck so that it would dig in at front, lift at stern as we applied quite a bit of power as it dug in when the free surface affect of the water rushed forward.

I don't think it would work well on a Cat as you don't have the hull resistance of a barge to cause it to dig in and dive.....Also bridle damage to topsides would be immense.

If salvaging without a crane, I would tow to shallow water that accommodated the mast, (if still there. and then remove the mast and rigging for salvage later

Now able to move closer to shore , I would anchor 2 heavy strops to strong points on the bottom (rock outcrops) on the shore side hull .
Then set up heavy lift strops and tackle to shore winches on the offshore hull. (Winches stripped from the boat)

On day of flip, shorten hull anchor lines to bottom as much as possible at Low Tide.

Let incoming tide sink and flood that hull as much as possible, while you drain and lift with winches on the outboard hull to force the sinking hull even deeper

With luck and trial and error, cat should flip/roll over as she stays mostly in the water with less shear stress on the hulls.

I think a lot of the suggestions assume inherent buoyancy in the hulls. My thoughts are that (most) Cats over 30' do not have enough flotation built in to survive a fully flooded condition. That said, a flipped cat would likely lose enough air in the righting attempt that she would sink as fast as any other boat.

Having done quite a bit of salvage, were I tasked with righting a large cat (with no budget), I would install air bags in each hull. I would fully fill the bags on the highest hull, and do my best to remove any residual air in the lowest. I would then rig lift bags outboard the lower hull on the side to which I wish to rotate. The boat "should" then roll to a semi-upright position, at which point I would begin inflating the submerged hull's air bags. The internal bags would remain inflated until a crane was available.

As others have mentioned, the salvage and subsequent repairs would far exceed the cost of a new boat, AND you would likely still have a boat that has been stressed well beyond design limits in its initial roll.

__________________Any fool with a big enough checkbook can BUY a boat; it takes a SPECIAL type of fool to build his own! -Capngeo

The owner of the boat I race on was helming another boat on an offshorerace on their way to Hammo recently. He was off shift at the time but their mast snapped; the spinnie pole took out the forestay on a less than controlled move in the early evening. It was a disaster and they nearly holed the boat with the rigging dragging a splintered carbon mast alongside bouncing off the hull. They were very lucky.

I absolutely recognise that capsize=bad but just how much better is the mast snapping? Perhaps a lot better, if no one is near it at the time and it doesn't punch a hole in the cabin top and kill someone. Or hole the boat. Most modern cats likely have enough buoyancy to not sink but it won't be a pleasant experience...

The owner of the boat I race on was helming another boat on an offshore race on their way to Hammo recently. He was off shift at the time but their mast snapped; the spinnie pole took out the forestay on a less than controlled move in the early evening. It was a disaster and they nearly holed the boat with the rigging dragging a splintered carbon mast alongside bouncing off the hull. They were very lucky.

I absolutely recognise that capsize=bad but just how much better is the mast snapping? Perhaps a lot better, if no one is near it at the time and it doesn't punch a hole in the cabin top and kill someone. Or hole the boat. Most modern cats likely have enough buoyancy to not sink but it won't be a pleasant experience...

A good discussion point or two methinks, your thoughts?

Spinnaker pole on the forestay in a decent wind is always a good recipe for the mast coming down. It only takes a moment. Seems to happen once every race season here in Annapolis to someone or other. When masts do break,90% of the time they break where the lowers connect and it's more a tangled mess than anything. So it's not like frogs in a blender in the cabin.

Personally, I'll take the mast coming down over capsizing in a cat, particularly 500 miles offshore. It's the possibility of someone getting hurt but being able to get back home vs. the possibility of someone getting hurt AND everyone then drowning or expiring from exposure afterwards.

They had time to dump the main and turn down there, IMO. Not sure what really happened on board but then they were pushing and testing a prototype. IIRC, dumping the traveller involved foot pedals? Maybe as simple as lost footing? Who knows

Spinnaker pole on the forestay in a decent wind is always a good recipe for the mast coming down. It only takes a moment. Seems to happen once every race season here in Annapolis to someone or other. When masts do break,90% of the time they break where the lowers connect and it's more a tangled mess than anything. So it's not like frogs in a blender in the cabin.

Personally, I'll take the mast coming down over capsizing in a cat, particularly 500 miles offshore. It's the possibility of someone getting hurt but being able to get back home vs. the possibility of someone getting hurt AND everyone then drowning or expiring from exposure afterwards.

Fair call. I haven't looked that closely but with the wider chain plates on a cat is there more chance of a mast snapped low to do more damage to the cabin top etc? I'm not sure.

I agree that the risk of drowning or expiring from exposure is higher after capsize but I wonder by how much. Of course it's all likely moot and best saved for a conversation with an actuary over an absinthe or seven...but I have an intellectual curiosity...

I am both a rigger and a salvor, and very occasionally a builder of multihulls.
Those multis that I have righted from inversion I have done so by longitudinal flip, always stern over bow. It is surprising how little energy is needed to achieve this.
It is not true that rigs on production cats are designed to fail on inversion. While the stresses are enormous and failure frequently does occur in such instances there is no design requirement for this.